1. Field of the Invention
This invention relates to a method and apparatus for winding a segmented stator or rotor of an electromechanical device, such as an electric motor or generator. In a particularly preferred embodiment, the invention relates to a method and apparatus for winding a segmented stator or rotor in which multiple segments for one phase are wound as a set, and then combined with other sets of wound segments for the remaining phases of the motor or generator.
2. Description of Related Art
Electromechanical devices such as motors and generators comprise a stator and a rotor that rotates relative to the stator. In all such devices, either the stator or the rotor (or both) comprises windings that determine basic characteristics of the device.
Focusing for example on a stator of an electric motor, the stator is provided with a number of windings that is determined by the number of phases of the motor. For example, a three phase motor has a stator with three windings. Each of the windings further comprises 2N poles per winding, where N is an integer equal to or greater than one. For example, a three phase four pole motor comprises a total of twelve poles. Each pole further includes one or more coils, with each coil being formed of numerous turns of wire wound around a common bobbin structure.
Various techniques are known for constructing a stator of an electric motor. For example, according to one known technique, the stator is constructed using a large number of very thin laminations that, when stacked together, produce a stator structure that is generally cylindrically shaped with but with bobbin structures that extend the length of the cylinder and that protrude radially inwardly. The bobbins are then each wound with wire to form respective stator coils using a needle-based winding machine that is placed at the center of the stator structure.
A recognized problem with this approach is that the amount of wire that can be provided on each bobbin is limited by the fact a certain amount of space is required for the operation of the winding machine. During the winding operation, the needle travels in the slots that are between the bobbins and, as wire fills the slots, the amount of space left for the needle to travel decreases. The winding operation ends when there is not enough room left in the slots for the needle to travel. At this time, however, the slots are not completely filled with wire, resulting in unutilized space (i.e., incomplete slot fill) once the winding operation is complete. In general, it is desirable to have as many turns of wire as possible in the space provided (i.e., maximum slot fill) in order to maximize the torque and speed characteristics of the motor.
A recognized solution to this problem is to utilize what is referred to in the art as a segmented stator. According to this approach, the stator is constructed using a plurality of segments each of which defines a bobbin upon which wire is wound to form one of the coils of the motor. Each segment is generally T-shaped when viewed from one end of the motor, with the bottom (vertical) leg of the T forming the bobbin upon which wire is wound to form one of the coils of the motor, and the top (horizontal) leg of the T being joined end to end with the top legs of the other T-shaped segments in the shape of a circle, thereby resulting in a circular stator when viewed from one end of the motor. This construction technique therefore results in a stator with an overall shape that is the same as that of an unsegmented stator.
The use of a segmented stator allows for complete slot fill because each segment can be wound individually before being physically combined with the remaining stator segments. As a result, there are no space restrictions to interfere with the operation of the winding machine and to thereby prevent each segment from being completely wound.
However, the fact that the segments are wound individually also requires an increased number of connections that must be made using manual techniques, thereby leading to increased human error in the construction process. Because the segments are wound individually, the various coils must be connected once the stator segments are combined. The coils are not simply all connected in series or parallel but rather are connected according to intricate connection patterns. For example, for a three phase motor, the coils for each phase are connected in series in alternating fashion around the motor, and the windings that are thereby formed are then connected in either a wye or a delta configuration. Even the most careful individuals are prone to making mistakes when trying to connect the various coils in the correct manner. Of course, connecting the coils in an incorrect manner results in a defective motor.
Thus, a system and method of constructing a wound member of an electromechanical device that utilizes a segmented construction technique, but that also avoids the need for the increased number of manual connections that are required by the segmented construction techniques described above, would be highly advantageous.